Nonwoven openwork net structure of thermoplastic material

ABSTRACT

A nonwoven netlike openwork structure of thermoplastic material is provided, comprising a plurality of bosses arranged in a plurality of rows extending substantially uniformly throughout the structure, substantially all of which bosses are integrally joined to at least two other such bosses by bands of thermoplastic material, said bosses being of at least two different configurations, and the area of the structure between the bosses and the bands being substantially devoid of thermoplastic material. If desired the structure may also include portions in which all the bosses are of substantially the same configuration.

States ant Inventors James Dow Thaxted, Essex; Albert George Patchell,Welwyn Garden City; Ronald Lloyd, Sawbridgeworth, all of England Appl.No. 807,884 Filed Mar. 17, 1969 Patented Oct. 26, 1971 Assignee T. J.Smith 8: Nephew Limited Hull, England Priority Mar. 20, 1968 GreatBritain 13411/68 NONWOVEN OPENWORK NET STRUCTURE OF THERMOPLASTICMATERIAL 11] Claims, 8 Drawing Figs.

11.8. C1 161/113, 161/138,264/154,264/289 1nt.Cl B32b 3/10 lField ofSearch 161/89, 130-131, 109, 117, 122, l 13, 138; 264/289, 293, 288,154

[56] Reierences Cited UNITED STATES PATENTS 3,137,746 6/1964 Seymour eta1. 264/73 3,387,077 6/1968 Sammons et al.... 161/89X 1,984,653 12/1934Palmeretal 161/131 X 2,958,148 11/1960 Sylvester et a1 264/293 X PrimaryExaminer-Philip Dier Att0rneySinger, Stern & Carlberg ABSTRACT: Anonwoven netiike opeznwork structure ofthermoplastic material isprovided, comprising a plurality of bosses arranged in a plurality ofrows extending substantially uniformly throughout the structure,substantially all of which bosses are integrally joined to at least twoother such bosses by bands of thermoplastic material, said bosses beingof at least two different configurations, and the area of the structurebetween the bosses and the bands being substantially devoid ofthermoplastic material. If desired the structure may also includeportions in which all the bosses are of substantially the sameconfiguration.

PATENTEUUET 25 1911 SHEET 2 OF 6 FIG. 3.

PATfiNTEDum 26 Ian PATENTEDnm 25 IS?! j 3,516,154

SHEET E OF 6 NONWOVEN OPENWORK NET STRUCTURE OF THERMOPLASTICMATElRllAlL The present invention relates to a netlike openworkstructure of a thermoplastic material and to methods for the productionof such an openwork net.

According to one embodiment of the present invention there is provided anonwoven netlike openwork structure of thermoplastic material,comprising a plurality of bosses arranged in a plurality of rowsextending substantially uniformly throughout the structure,substantially all of which bosses are integrally joined to at least twoother such bosses by bands of thermoplastic material, said bosses beingof at least two different configurations, and the area of the structurebetween the bosses and the bands being substantially devoid ofthermoplastic material.

Preferably substantially all of said bosses are integrally joined to atleast four other such bosses by bands of thermoplastic material.

Where reference is made to bosses of different configuration it isintended that the bosses may be different in at least one, andpreferably all, of the following features, viz, shape, size andthickness.

it will be clearly understood that where reference is made throughoutthe specification including the claims, to the rows of bosses extendingsubstantially uniformly" it is not intended that each row of bosses isidentical, but that, where all the rows are not identical, the rows arearranged in a repeating pattern.

In some embodiments of the invention the bands may be of two or moredifferent thicknesses depending upon the material from which they areproduced. For example some of the bands may be of one thickness and theremainder of the bands may be of another thickness.

ln one preferred embodiment of the present invention the netlilteopenwork structure comprises a plurality of octagonally shaped bossesarranged in a regular pattern one at each intersection of an imaginarysquared lattice or grid and a plurality of square-shaped bosses,arranged in a regular pattern one at the center of each square of saidimaginary lattice or grid.

In this preferred form of the invention, each of the squareshaped bossesis connected to four adjacent octagonally shaped bosses and eachoctagonally shaped thickened area is connected to four square-shapedbosses, and to four octagonally shaped bosses.

in another preferred embodiment the netlike openwork structure comprisesa regular pattern of octagonal bosses, hexagonal bosses and squarebosses all interconnected by bands of thermoplastic material.

In yet a further preferred embodiment the netlike openwork structurecomprises a regular pattern of a plurality of square bosses and aplurality of bosses each of which is shaped like two squares spacedapart butjoined by a connecting piece.

In a further preferred embodiment of the invention the netlike openworkstructure comprises a regular pattern of bosses of two differentconfigurations, the bosses of one configuration being approximatelysquare and each being integrally connected by bands to eight smallersubstantially square bosses, each of said smaller bosses beingintegrally connected to two of said larger bosses and to two saidsmaller bosses.

An openworlr structure of the present invention may in one embodiment beproduced by the biaxial stressing of a sheet of thermoplastic materialhaving a regular pattern of bosses of at least two differentconfigurations on at least one surface thereof, until the material takeson a degree of permanent set and splits occur in the thinner material.

The openwork structure of the invention may in another embodiment beproduced by biaxially stressing a sheet of thermoplastic material havinga regular pattern of separate bosses of at least two differentconfigurations on at least one surface thereof. until the material takeson a degree of permanent set and splits occur in the thinned material.

In yet a further embodiment the openwork structure of the invention maybe produced by biaxially stressing a sheet of thermoplastic materialcomprising at least one portion having a regular pattern of bosses of atleast two different configurations on at least one surface thereof andat least one other portion having a regular pattern of substantiallyidentical bosses on at least one surface thereof until the materialtakes a degree of permanent set and splits occur in the thinnedmaterial.

The material in between these bosses on biaxial stressing, splits toform the connecting strands. The biaxial stressing may be carried outsequentially or simultaneously and the two directions of stretch arepreferably at right angles.

In one form the thermoplastic starting material may be formed withbosses raised above the surface of the sheet material. Alternatively thesheet may have a plurality of cavities formed therein, in such a manneras to leave a plurality of portions or bosses which are of fullthickness of the sheet.

Various methods of sequentially and simultaneously stressing thethermoplastic material to form the openwork structure of the presentinvention are described in Patent specifications Nos. 914,489; 1,055,963and 1,075,487. These methods may be adapted to produce material of thepresent invention. 7

According to another embodiment of the present invention there isprovided a nonwoven netlilte openwork structure of thermoplasticmaterial, comprising at least one portion having a plurality of bossesarranged in a plurality of rows extending substantially uniformlythroughout said at least one portion, substantially all of which bossesare integrally joined to at least two other such bosses by bands ofthermoplastic material, said bosses being of at least two differentconfigurations; and at least one other portion having a plurality ofbosses arranged in a plurality of rows extending substantially uniformlythroughout said at least one other portion, substantially all of whichbosses are integrally joined to at least two other such bosses by bandsof thermo plastic material, all said bosses in said at least one otherportion being of substantially the same configuration; and the area ofthe structure between the bosses and the bands being substantiallydevoid of thermoplastic material.

According to the last described embodiment openwork structures may thusbe formed having areas of differing degrees of openness thereby allowingthe formation of openwork structures of lacelike appearance.

In this latest embodiment, the structure of the portion or portionshaving bosses of at least two different configurations (i.e. theirregular part of the openwork structure is preferably as described inthe above preferred embodiment of the invention. The portion or portionshaving bosses of substantially identical configuration (i.e. the regularpart of the structure) may be produced from portions of startingmaterial having a configuration similar to the starting materialsdescribed in G. B. Patent specifications Nos. 914,489; 1,055,963 and1,075,487 i.e. material having a plurality of embossments on of cavitiesin at least one surface thereof, Each boss in said at least one otherportion is preferably integrally joined to four or six other such bossesby bands of thinner material.

It will be apparent that in all versions of the invention the startingmaterial may if desired include a mixture of bosses, raised above atleast one surface of the sheet material, and cavities formed in at leastone surface of the sheet material.

The openworlt structures, of the present invention have many usesincluding use for decorative purposes eg. as curtain material and astable clothes etc.

The present invention will now be described by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a plan view of part of a sheet of thermoplastic material fromwhich an openwork structure of the present invention may be produced,

FIG. 2 is part of an openwork structure produced from sheet materialshown in FIG. 1,

FIG. 3 is a plan view of part of a sheet of thermoplastic material fromwhich another openworlr structure of the present invention may beproduced,

FIG. 4 is part of an openwork structure produced from the 3 sheetmaterial shown in FIG. 3,

FIG. 5 is a plan view of part of a sheet of thermoplastic material fromwhich yet another openwork structure of the present invention may beproduced,

FIG. 6, is part of an openwork structure produced from the sheetmaterial shown in FIG. 5,

FIG. 7 is a plan view of a part of a sheet of thermoplastic materialfrom which a further openwork structure of the invention may beproduced, and

FIG. 8 is an openwork structure produced from sheet material.

Referring to FIG. 1 of the drawings, a sheet of thermoplastic material10 has formed thereon allover pattern of a plurality of octagonal-shapedbosses, 12, arranged in a regular pattern, one at each intersection ofan imaginary squared lattice or grid (shown in dotted lines) and aplurality of square-shaped bosses 14 located one at the center of eachof the squares of said imaginary lattice. Each octagonal-shaped boss 12is of symmetrical shape, alternate sides being of shorter and longerlength. Each of the shorter sides of the octagonal-shaped bosses 12 isthe same length as the sides of the square-shaped bosses l4 and islocated adjacent to and facing one of the sides of a square-shaped boss14. Each of the longer sides of each octagonal-shaped boss 12 is locatedadjacent to and facing one of the longer sides of an adjacentoctagonal-shaped boss 12. The distance between the centers of twoadjacent octagonal-shaped bosses is 0.040 inches and each side of thesquare-shaped boss is 0.010 inches long. The sides 16 of theoctagonal-shaped bosses l2, and the sides 18 of the squareshaped bosses,slope such that the base of each boss is of greater area than the mostraised portions thereof. The bosses may be formed in the thermoplasticmaterial using a profiled roller rotating on an axis at 45to the dottedlines indicating the lattice or grid. Each of the bosses is surroundedby an area of material 20, which is thin by comparison with the embossedportions.

To produce the openwork structure shown in FIG. 2, the sheet materialshown in FIG. 1 is biaxially stressed either sequentially orsimultaneously in the directions of the two arrows indicated in FIG. 1.

On biaxial stressing the thinner material 20 surrounding and joining thebosses becomes stretched to such an extent that it splits leaving bands22 of material joining the bosses together. Each square-shaped boss 14is connected by bands 22 to four octagonal-shaped bosses l2 and eachoctagonal-shaped boss 12 is connected by bands 22 to four square-shapedbosses l4 and four octagonal-shaped bosses 12.

Referring to FIG. 3 a sheet of thermoplastic material 30 has formedthereon an allover regular pattern of octagonal-shaped bosses 32,hexagon-shaped bosses 34, and square-shaped bosses 36 and 36a. Thearrangement of the embossments is similar to that of FIG. 1 with thefollowing two exceptions i. the octagonal-shaped bosses are regular ii.alternate octagonal-shaped bosses of the arrangement of FIG. 1 aredivided into a central square-shaped boss 36a surrounded by fourhexagonal-shaped bosses 34.

The bosses as in FIG. 1 may be formed in the thermoplastic materialusing a profiled roller rotating on an axis as indicated by the dottedline. Each of the bosses is surrounded by an area 40, which is thin bycomparison with the bosses.

On biaxially stressing either simultaneously or sequentially in thedirection of the two arrows, an openwork structure, such as that shownin FIG, 4, is produced.

To shown clearly the way in which the sheet material of FIG. 3 forms theopenwork structure of FIG. 4, five octagonal bosses 32 have been markedA, B, C, D and E in FIG. 3 and these same five bosses are marked in asimilar manner in FIG. 4.

It can be seen from FIG. 4 that each of the bosses is connected to anumber of other bosses by bands 42 of thermoplastic material. Eachoctagonal-shaped boss 32 is connected by the bands 42 to two otheroctagonal-shaped bosses '32, four square-shaped bosses 36, and fourhexagon-shaped bosses 34. Each square-shaped boss 36 is connected bybands 42 to two octagonal-shaped bosses 32, and two hexagonalshapedbosses 34. Each square-shaped boss 36a is connected to fourhexagonal-shaped bosses 34. Each hexagonal-shaped boss 34 is connectedby bands 42 to one square-shaped boss 36, one square-shaped boss 36a,one octagonal-shaped boss 32 and three hexagonal-shaped bosses 34.

Referring to FIG. 5, a sheet of thermoplastic material 50 has formedthereon allover regular pattern (only part of which is shown) of bosses52 and 54 of two different configurations. The bosses 52 are square inshape and the bosses 54 have the shape in plan view of two squaresoverlapping at the one corner. Each of the bosses is surrounded by anarea 56 of thermoplastic material which is thin by comparison with thebosses 52, 54.

The bosses 52, 54 may be formed in the thermoplastic material using aprofiled roller rotating on an axis as indicated by the dotted line.

On biaxial stressing either simultaneously or sequentially in thedirection of the two arrows shown an openwork structure, such as thatshown in FIG. 6, is produced.

To show clearly the way in which the sheet material of FIG. 5 forms theopenwork structure of FIG. 6, the two ends of each of the four bosses 54shown have been referenced A,A,B ,B,C,C,and D,D,and the one square boss52 shown has been referenced X.

In the openwork structure of FIG. 6 it can be seen that the two ends ofeach boss 54 have been moved apart and are joined by a connecting piece58 which may be considered either as part of a single boss or as a bandof material joining two bosses. Each end of bosses 54 is connected bybands 60 of thin material (thinner than connecting pieces 58) to one endof each of two other bosses 54 and to two sqaure-shaped bosses 52.

This particular arrangement provides an openwork structure in which ineffect two bosses (i.e. the two ends ofa boss 54) are produced from asingle boss in the unstressed film, in which the bands 60 may be ofdifferent width and thickness to the connecting pieces 58 and in whichconnecting pieces 58 are formed from a part of a boss which on theunstressed film is of less width than other parts of the same boss.

Referring to FIG. 7, a sheet of thermoplastic material 70 has formedthereon an allover regular pattern of conical depressions 72 arranged inrows both 45 directions to the transverse direction of the sheetmaterial, (indicated by dotted line). Any pair of adjacent rows consistsof (i) a continuous row of conical depressions 72 and (ii) a row ofconical depressions 72 where every fourth depression is omitted. Thisarrangement results in boss-forming areas 74 and 76 having the fullthickness of the sheet material) of 2 distinct shapes. Boss formingareas 74 are of approximately square shape with the sides of the squareslightly concave and are each surrounded by 4 strand-forming regions 78of roughly triangular cross section.

Boss-forming areas 76 are of approximately maltese crossshape and areeach surrounded by 8 strand-forming regions 78 of roughly triangularcross section.

The pattern of conical depressions 72 may be formed in the thermoplasticmaterial using a profiled roller rotating on an axis as indicated by thedotted line.

On biaxial stressing either simultaneously or sequentially in thedirection of the 2 arrows shown, an openwork structure such as shown inFIG. 8 is produced. During the biaxial stressing the strand-fonningregions 78 become attenuated and holes appear at the bottoms of theconical depressions 72 at a fairly early stage in the stressingoperation. As the stressing continues, the hole thus formed enlargesprogressively between the strand-forming regions 78 as they become moreattenuated.

Referring to FIG. 8, when the biaxial stressing ceases an openworkstructure as depicted is obtained in which each small boss 80 (formedfrom boss-forming areas 74 in FIG. 7)

EXAMPLE I A high-density polyethylene was extruded to form a sheethaving a pattern as shown in FIG. ll of the drawings and having thefollowing dimensional characteristics:

Thickness of large oct. bosses ll2=0.007 in.

Thickness ofsmall square bosses 14=0.005 in.

Thickness ofthinner material =0.0023 in.

Distance between centers of two adjacent oct. bosses l2=0.040 in.

Length of side (at base) ofsquare boss lkin. ins.

The sheet was stretched in the following sequence,

i. percent in the machine direction ii. 150 percent in the transversedirection iii. 100 percent in the machine direction An openworkstructure having a geometry as shown in FIG. 2 of the drawings wasobtained in a yield at 30 square yards per pound. The structure had thefollowing physical characteristics:

Tensile strength (lbs./in.) MD 4.l

Tear strength (g.) MD 80 Brust strength (p.s.i.) l2

EXAMPLE II A polypropylene polymer was extruded into a sheet andembossed with a pattern as shown in FIG. 7 of the drawings. The sheethas the following dimensional characteristics:

Thickness of sheet =0.0ll I in.

Diameter ofmouth ofconical depression 72=0.020 in.

Depth of conical depression 72=0.0l0 in.

Distance between centers of adjacent depressions =0.028

m. The sheet was then stretched in the following sequence,

i. 70 percent in the machine direction ii. 200 percent in the transversedirection iii. 80 percent in the machine direction An openwork structurehaving a geometry as shown in FIG. it was obtained. The structure hadthe following physical characteristics:

Tensile (lbs/in.) MD l2.7 TD l3.2 Tear trength (g.) MD 210 TD 200 Burststrength (p.s.i.) 29

We claim:

l. A nonwoven openwork net structure of thermoplastic material,comprising a plurality of bosses arranged in a plurality of rowsextending substantially uniformly throughout the structure, and bands ofthermoplastic material integrally joining substantially all of saidbosses to at least two other bosses, said bosses being of at least twodifferent configurations, and the area of the structure between thebosses and the bands being substantially devoid of thermoplasticmaterial.

2. A structure according to claim 1, wherein all of said bosses areintegrally joined to at least four other bosses by bands ofthermoplastic material.

3. A structure according to claim 1, comprising a plurality ofoctagonally shaped bosses arranged in a regular pattern one at eachintersection of an imaginary squared lattice or grid, and a plurality ofsquare-shape bosses, arranged In a regular pattern one at the center ofeach square of said imaginary lattice or grid, each of thesquare-shaped. bosses being connected to four adjacent octagonallyshaped bosses and each octagonally shaped boss being connected to foursquare-shaped bosses and to four octagonally shaped bosses.

4. The structure according to claim 1, comprising a regular pattern ofoctagonal bosses, hexagonal bosses and square bosses all interconnectedby bands of thermoplastic material.

5. A structure according to claim 1, comprising a regular pattern of aplurality of square bosses and a plurality of bosses each of which isshaped like two squares spaced apart but joined by a connecting piece.

6. A structure according to claim 1, comprising a regular pattern ofbosses of two different configurations. the bosses of one configurationbeing approximately square and each being integrally connected by bandsto eight smaller substantially square bosses, each of said smallerbosses being integrally connected to two of said larger bosses and twoof said smaller bosses.

7. A structure according to claim I, wherein the bands joining thebosses are of different thickness.

8. A nonwoven openwork net structure of thermoplastic material,comprising at least one portion having a plurality of bosses arranged ina plurality of rows extending substantially uniformly throughout said atleast one portion and bands of thermoplastic material integrally joiningsubstantially all of said bosses to at least two other bosses, saidbosses being of at least two different configurations; and at least oneother portion having a plurality of bosses arranged in a plurality ofrows extending substantially uniformly throughout said at least oneother portion, and bands of thermoplastic material integrally joiningsubstantially all of said bosses; to at least two other bosses, all saidbosses in said at least one other portion being of substantially thesame configuration, and the area of the structure between the bosses andthe bands being substantially devoid of thermoplastic material.

9. A structure according to claim 8, wherein each boss in said at leastone other structure is integrally joined to four or six other suchbosses by bands of thinner material.

10. A method of producing an openwork net structure of thermoplasticmaterial comprising a plurality of bosses which are of at least twodifferent configurations and arranged in a plurality of rows extendingsubstantially uniformly throughout the structure with bands integrallyjoining substantially all of said bosses to at least two other bosses,said method comprising biaxially stressing a sheet of thermoplasticmaterial having a regular pattern of bosses of at least two differentconfigurations on at least one surface thereof, until the material takeson a degree of permanent set and splits occur in the thinned material.

2. A structure according to claim 1, wherein all of said bosses are integrally joined to at least four other bosses by bands of thermoplastic material.
 3. A structure according to claim 1, comprising a plurality of octagonally shaped bosses arranged in a regular pattern one at each intersection of an imaginary squared lattice or grid, and a plurality of square-shaped bosses, arranged in a regular pattern one at the center of each square of said imaginary lattice or grid, each of the square-shaped bosses being connected to four adjacent octagonally shaped bosses and each octagonally shaped boss being connected to four square-shaped bosses and to four octagonally shaped bosses.
 4. The structure according to claim 1, comprising a regular pattern of octagonal bosses, hexagonal bosses and square bosses all interconnected by bands of thermoplastic material.
 5. A structure according to claim 1, comprising a regular pattern of a plurality of square bosses and a plurality of bosses each of which is shaped like two squares spaced apart but joined by a connecting piece.
 6. A structure according to claim 1, comprising a regular pattern of bosses of two different configurations, the bosses of one configuration being approximately square and each being integrally connected by bands to eight smaller substantially square bosses, each of said smaller bosses being integrally connected to two of said larger bosses and two of said smaller bosses.
 7. A structure according to claim 1, wherein the bands joining the bosses are of different thickness.
 8. A nonwoven openwork net structure of thermoplastic material, comprising at least one portion having a plurality of bosses arranged in a plurality of rows extending substantially uniformly throughout said at least one portion and bands of thermoplastic material integrally joining substantially all of said bosses to at least two other bosses, said bosses being of at least two different configurations; and at least one other portion having a plurality of bosses arranged in a plurality of rows extending substantially uniformly throughout said at least one other portion, and bands of thermoplastic material integrally joining substantially all of said bosses to at least two other bosses, all said bosses in said at least one other portion being of substantially the same configuration, and the area of the structure between the bosses and the bands being substantially devoid of thermoplastic material.
 9. A structure according to claim 8, wherein each boss in said at least one other structure is integrally joined to four or six other such bosses by bands of thinner material.
 10. A method of producing an openwork net structure of thermoplastic material comprising a plurality of bosses which are of at least two different configurations and arranged in a plurality of rows extending substantially uniformly throughout the structure with bands integrally joining substantially all of said bosses to at least two other bosses, said method comprising biaxially stressing a sheet of thermoplastic material having a regular pattern of bosses of at least two different configurations on at least one surface thereof, until the material takes on a degree of permanent set and splits occur in the thinned material. 